1. Field of the Invention
The present invention relates to an inkjet printing apparatus, more particularly, to the inkjet printing apparatus that executes a suction-recovery action by using a tube pump.
2. Description of the Related Art
A printing apparatus is known in which an ejection opening face formed with an ejection opening of an inkjet printing head is sealed with a cap, a suction unit such as a pump connected to the cap is activated, and air bubbles and ink having an increased viscosity are suctioned and ejected from an inside or the like of the ejection opening, with the result that ejection performance is recovered.
Japanese Patent Laid-Open No. 2002-036604 discloses a printing apparatus using a tube pump as the suction unit. An axis of a roller in the tube pump of Japanese Patent Laid-Open No. 2002-036604 is supported by a holder so as to be able to be moved between a pressing position where a tube is pressed and a non-pressing position where the tube is not pressed, along a groove having a long-hole geometry formed in the holder. In a configuration according to Japanese Patent Laid-Open No. 2002-036604, the roller presses the tube along with rotation of the holder in one direction and squeezes the tube to thereby exert a pump function, and in the case where the holder is rotated and driven in another direction, the roller is moved toward the non-pressing position.
However, in the configuration according to Japanese Patent Laid-Open No. 2002-036604, since the roller is moved along the groove having the long-hole geometry, the tube may be pressed by the roller to thereby generate a backflow of the fluid flowing from the pump to the cap, until the roller reaches the non-pressing position at the time of rotation of the holder in another direction. In the case where the fluid flowing back reaches the cap, the air bubbles are generated in ink in the cap, and a mixed color in which inks having different colors are mixed may be generated by the contact of the air bubbles with the ejection opening. Furthermore, meniscus formed at the ejection opening is destroyed by the air bubbles to thereby cause gas to flow in the ejection opening, and there may be generated the non-ejection of ink, in which ink is not ejected but the gas is ejected from the ejection opening. As described above, in the case where the backflow of the fluid flowing from the pump to the cap occurs, ink in a desired color may not be applied to a printing medium, or ink may not be applied thereto, with the result that image quality may be deteriorated.